Subaru Spectroscopy of the Interacting Type Ia Supernova SN 2002ic: Evidence of a Hydrogen-rich, Asymmetric Circumstellar Medium

Abstract

Optical spectroscopy of the Type Ia supernova SN 2002ic obtained on 2003 June 27.6 UT, i.e., ~222 rest-frame days after explosion, is presented. Strong H emission indicates an interaction between the expanding SN ejecta and an H-rich circumstellar medium (CSM). The spectrum of SN 2002ic resembles those of SNe 1997cy and 1999E. The three SNe also have similar luminosities, suggesting that they are the same phenomenon and that the CSM is also similar. We propose a new classification, Type IIa SNe, for these events. The observed line profiles and line ratios are measured and discussed within the ejecta-CSM interaction scenario. The emission in H Balmer, [O III], and He I lines, and in permitted Fe II blends, resembles the spectra of the Type IIn SN 1987F and of Seyfert 1 galaxies. A high-density, clumpy CSM is inferred. Strong, very broad [Ca II]/Ca II and [O I]/O I emissions imply that not all the outer SN ejecta were decelerated in the interaction, suggesting that the CSM is aspherical.